Patent Issued for SD Switch Box in a Cellular Handset

By a News Reporter-Staff News Editor at Journal of Engineering -- From Alexandria, Virginia, VerticalNews journalists report that a patent by the inventors Sherman, Itay (Hod Hasharon, IL); Bychkov, Eyal (Hod Hasharon, IL); Segalov, Yaron (Tel Aviv, IL), filed on June 27, 2011, was cleared and issued on December 4, 2012.

The patent's assignee for patent number 8327124 is Google Inc. (Mountain View, CA).

News editors obtained the following quote from the background information supplied by the inventors: "Today's conventional cellular handset includes a cellular base band modem. The base band modem does not have built-in non-volatile memory, and has limited internal volatile memory (SRAM). For use of non-volatile memory, a cellular modem may be connected to a NOR flash memory, and also to additional external SDRAM.

"When booting up, a cellular modem generally accesses the NOR flash memory to execute a code image that is stored therein. The cellular modem may access such code image directly, or by first copying it to its internal SRAM.

"Many cellular modems also support a peripheral boot mode, through which they load a secondary code image from an external port, such as a UART port or a USB port, which is connected to an external device, such as a PC computer, which loads the secondary code image via a peripheral interface. The secondary code image is then used to re-program the NOR flash memory with new image code. Peripheral boot mode is typically used for program development and debugging via a PC.

"High end cellular handsets also have NAND flash memory coupled thereto. In such case, the NAND flash memory is used for code and data storage. The NAND flash memory is connected via a dedicated NAND controller embedded in the cellular base band modem, or via an SD bus to an external SD controller that is connected to the NAND flash. For cellular handsets that have NAND flash memory, access to the NAND flash is performed via the cellular base band modem.

"Cellular handsets may support connection to an external device host, such as a PC computer. In such case, the handset provides the host access to its internal NAND flash memory. Host access to NAND flash memory is generally performed over a USB connection, where the internal NAND memory is mapped as a mass storage drive on the host. The handset thus operates as a USB device, which is a slave, and the host operates as a USB host, which is a master.

"Reference is now made to FIG. 1, which is a simplified block diagram of a prior art cellular handset 100. Handset 100 includes a cellular base band modem 110 with an external memory interface (EMIF) 120 for accessing a NAND flash storage 130 and an SDRAM storage 140. Correspondingly, EMIF 120 includes a NAND controller 150 and an SDRAM controller 160, respectively.

"Many consumer electronic (CE) devices, such as MP3 song players and MP4 movie players, support connection to non-volatile storage elements, the most common storage element being SD memory and its variants including inter alia Mini SD and Micro SD. The CE device operates as a host, which is a master, and the SD memory operates as a slave.

"It would thus be desirable to be able to connect CE devices that support SD connections with cellular modems, in order to enhance the CE devices with modem functionality. However, many challenges have to be overcome in doing so. Some of these challenges are: How is the cellular modem booted up? How does the CE device communicate with the cellular modem? How is the cellular modem transition in and out of sleep mode carried out? How are conflicts resolved when both the CE device and the cellular modem want to access SD memory at the same time?"

As a supplement to the background information on this patent, VerticalNews correspondents also obtained the inventors' summary information for this patent: "Aspects of the present invention concern a design for a cellular handset that is connected to a CE host device, and enhances the CE device with modem functionality. The CE host device supports SD connection. Examples of such host devices abound and include inter alia digital cameras, personal data assistants (PDAs), MP3 music players, MP4 movie players, TVs with SD slots, laptop PCs and GPS navigational systems.

"In addition to enhancing the CE host with modem functionality, connection of the cellular handset to the CE host also serves to enhance the host with the storage capabilities of the modem.

"The special design of the present invention enables a cellular base band modem within the handset to bypass NOR flash memory when booting up, enables communication between the cellular base band modem and the CE host, and enables the cellular base band modem to switch in and out of sleep mode without loss of state parameters and code image.

"In accordance with an embodiment of the present invention, a convergence controller is used to couple the CE host device with the handset's cellular base band modem and with the handset's NAND flash memory. The convergence controller serves as an SD switch box, which connects two SD devices, namely, the cellular base band modem and the CE device, and enables switching access to SD storage between the two SD devices.

"The convergence controller includes a communication mechanism through which the cellular base band modem and the CE host device communicate with one another. Such communication mechanism includes a first mailbox via which the cellular base band modem sends a message to the CE host, and a second mailbox via which the CE host sends a message to the cellular base band modem.

"The two mailboxes are used to resolve conflicts when both the CE host and the cellular base band modem want to access SD memory at the same time. The cellular base band modem sends an access request message to the CE host via the first mailbox, and the CE host responds by sending an access granted message to the cellular base band modem via the second mailbox.

"There is thus provided in accordance with an embodiment of the present invention a cellular handset, including a cellular base band modem, including a UART interface, and an SD host interface, a NAND flash memory, a NAND controller coupled with the NAND flash memory, a host device including a host controller, wherein the electronic host device supports an SD connection, and a convergence controller coupled with the cellular base band modem, the host device and the NAND controller, including a UART port for transferring data to and from the cellular base band modem via the UART interface, an SD port for transferring data to and from the cellular base band modem via the SD host interface, an SD port for transferring data to and from the NAND flash memory via the NAND controller, an SD port for transferring data to and from the host device via the host controller, a first mailbox into which the base band modem writes messages and from which the host device reads messages, and a second mailbox into which the host device writes messages and from which the cellular base band modem reads messages.

"There is additionally provided in accordance with an embodiment of the present invention a cellular handset, including a cellular base band modem, including a UART interface, and an SD host interface, a NAND flash memory, a host device including a host controller, wherein the electronic host device supports an SD connection, and a convergence controller coupled with the cellular base band modem, the host device and the NAND controller, including a UART port for transferring data to and from the cellular base band modem via the UART interface, an SD port for transferring data to and from the cellular base band modem via the SD host interface, a NAND controller coupled with the NAND flash memory, an SD port for transferring data to and from the host device via the host controller, a first mailbox into which the base band modem writes messages and from which the host device reads messages, and a second mailbox into which the host device writes messages and from which the cellular base band modem reads messages.

"There is moreover provided in accordance with an embodiment of the present invention a method for booting a cellular base band modem, including booting a cellular base band modem in a peripheral mode, reading a boot code image from a NAND flash memory, loading the boot code image to internal SRAM of the cellular base band modem, executing the boot code, by the cellular base band modem, loading a full code image from the NAND flash memory to the internal SRAM of the cellular base band modem, and accessing, by the cellular base band mode, the NAND flash memory via an SD port as a standard memory card.

"There is further provided in accordance with an embodiment of the present invention a method for communicating between a host device and a cellular base band mode, including requesting, by a cellular base band modem from a host device, access to an SD storage, including writing an access request message to a first mailbox, notifying the host device of the message in the first mailbox, including issuing an interrupt request to the host device, reading, by the host device, the message in the first mailbox, granting, by the host device, the access request, including writing a grant message to a second mailbox, wherein the grant message is the first block of a multi-block write, notifying the cellular base band modem of the message in the second mailbox, including issuing an interrupt request to the cellular modem, reading, by the cellular base band mode, the message in the second mailbox, including recognizing the first block as a grant message, holding an SD host bus in a busy state, thereby forcing the host device to hold and not access the bus, accessing, by the cellular base band modem, the SD storage, and upon completion of the accessing, removing the busy state from the SD host bus.

"There is yet further provided in accordance with an embodiment of the present invention a method for a cellular base band modem to transition in and out of a sleep mode, including when a cellular base band modem is idle for a long period of time: backing up state parameters in an internal SRAM, setting a secondary boot code as the code to be executed upon resumption of power, setting a timer for resumption of power, halting internal CPU operation, and disconnecting power to an external SDRAM, and when the timer has expired: reconnecting power to the external SDRAM, loading the secondary boot code, and loading a full code image to the external SDRAM."

For additional information on this patent, see: Sherman, Itay; Bychkov, Eyal; Segalov, Yaron. SD Switch Box in a Cellular Handset. U.S. Patent Number 8327124, filed June 27, 2011, and issued December 4, 2012. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=16&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=765&f=G&l=50&co1=AND&d=PTXT&s1=20121204.PD.&OS=ISD/20121204&RS=ISD/20121204

Keywords for this news article include: Google Inc.

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